Prediction and Realisation of High Mobility and Degenerate p-type Conductivity in CaCuP Thin Films

Joe Willis, Ivona Bravic, Rekha Schnepf, Karen Heinselman, Bartomeu Monserrat, Thomas Unold, Andriy Zakutayev, David Scanlon, Andrea Crovetto

Research output: Contribution to journalArticlepeer-review

15 Scopus Citations

Abstract

Phosphides are interesting candidates for hole transport materials and p-type transparent conducting applications, capable of achieving greater valence band dispersion than their oxide counterparts due to the higher lying energy and increased size of the P 3p orbital. After computational identification of the indirect-gap semiconductor CaCuP as a promising candidate, we now report reactive sputter deposition of phase-pure p-type CaCuP thin films. Their intrinsic hole concentration and hole mobility exceed 1 × 1020 cm−3 and 35 cm2 V−1 s−1 at room temperature, respectively. Transport calculations indicate potential for even higher mobilities. Copper vacancies are identified as the main source of conductivity, displaying markedly different behaviour compared to typical p-type transparent conductors, leading to improved electronic properties. The optical transparency of CaCuP films is lower than expected from first principles calculations of phonon-mediated indirect transitions. This discrepancy could be partly attributed to crystalline imperfections within the films, increasing the strength of indirect transitions. We determine the transparent conductor figure of merit of CaCuP films as a function of composition, revealing links between stoichiometry, crystalline quality, and opto-electronic properties. These findings provide a promising initial assessment of the viability of CaCuP as a p-type transparent contact.

Original languageAmerican English
Pages (from-to)5872-5883
Number of pages12
JournalChemical Science
Volume13
Issue number20
DOIs
StatePublished - 2022

Bibliographical note

Publisher Copyright:
© 2022 The Royal Society of Chemistry

NREL Publication Number

  • NREL/JA-5K00-83087

Keywords

  • DFT
  • p-type
  • phosphide
  • sputtering
  • transparent conductor

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